Now that all the fuss about modern-day sauropod dinosaurs has died down, we can get back to the serious business of vesper bats (incidentally, I do plan to cover the mokele-mbembe – in serious fashion – at some point in history). For previous parts in the vesper bats series, please look at the links below.

A group of about 17 species of American bats (occurring from Alberta down to Chile and Argentina) are known collectively as the hairy-tailed bats or hoary bats (Lasiurus*) (together with the Silver-haired bat Lasionycterus noctivagans, they’re also sometimes known as tree bats).

Most hairy-tailed bats are woodland animals that capture insects in flight, though Eastern red bats L. borealis at least will alight on vegetation to pick off insects. They are short-snouted with rounded ears that don’t extend beyond the limits of their thick pelt. They have high wing-loading and relatively slender wings and are fast, manoeuvrable fliers. [Adjacent painting of a Hoary bat L. cinereus by Carel Brest van Kempen (of Rigor Vitae), used with permission.]
* The generic name Lasiurus is also in use for a grass.

As is the case with many vesper bat genera, the taxonomic status of various populations has been the subject of debate, and certain populations currently regarded as species (including the Minor red bat L. minor, Pfeiffer’s red bat L. pfeifferi and Western red bat L. blossevillii) have been regarded as subspecies of other taxa in the past. A few South and Central American species have been discovered comparatively recently, like the Tacarcunan bat L. castaneus from Panama, named in 1960, the Cuban red bat, named in 1961, the Blackish red bat L. ebenus from Brazil, named in 1994, and Handley’s red bat L. atratus from Venezuela, Guyana, Surinam and French Guiana, named in 1996.

As suggested by their common collective name (and generic name*), hairy-tailed bats have thick fur covering the tail membrane and at least some species are well insulated from the cold: the Hoary bat in particular is well known for regularly flying when conditions are freezing (there is also a lot of fur on the wing membranes, even around the wrist). The tail membrane is used like a blanket during roosting, sometimes being folded right over the animal’s face as well as its chest and belly. Indeed, while most bats of temperate environments shelter inside tree hollows, buildings and caves, hairy-tailed bats roost and even hibernate outside, typically hanging from leaves or branches (roosting close to or even on the ground has been recorded too) [the adjacent photo, by Anne-Marie, shows an Eastern red bat hanging from a branch]. In what I presume is a further heat-saving adaptation, they often hang from just one foot.

* Lasiurus means ‘hairy tail’

There are some indications that the Eastern red bat has recently increased its Canadian range northward, perhaps as a result of climatic warming (Willis & Brigham 2003) [Eastern red bat photo above by USGS, from wikipedia]. A less well known species, the Southern yellow bat L. ega, might also have increased its range recently – this time in the south-western USA – thanks to increased roosting opportunities provided by newly planted ornamental palm trees (Spencer et al. 1988). This latter species is one of four or five species (the others are the Northern yellow bat L. intermedius, Western yellow bat L. xanthinus, Big red bat L. egregius and Cuban yellow bat L. insularis) once regarded as belonging to the separate ‘genus’ Dasypterus. These ‘yellow bats’ are not to be confused with the Scotophilus species, also sometimes called yellow bats, nor with the Rhogeessa bats, often called little yellow bats (I haven’t covered those groups yet).

The red ones

A few hairy-tailed bat species are notable for possessing reddish fur (sometimes described as brick red), and quite why they’re so red remains a good question (camouflage of some sort is the most popular explanation) [images below show the ventral and dorsal surfaces of a Western red bat photographed in Brazil. Note the thick pelt and large amount of fur on the wing – not just close to the body but also around the wrist. Images kindly provided by Guilherme Siniciato Terra Garbino]. All the more interesting is that Eastern red bats are generally thought to exhibit sexual dimorphism in coat colour, with males being redder than the reddish-grey females (e.g., Shump & Shump 1982): I mentioned this as a ‘fact’ when writing about red bats back in November 2007. Dimorphism in coat colour is really rare in mammals… lemurs and gibbons come to mind.

Anyway, Davis & Castleberry (2010) recently used museum specimens to show that – when body size and the time of year at which the animal was collected were taken into account – sex was less significant than the other two factors. Smaller individuals tend to be redder, and because males are generally smaller than females (recall the previous discussion of sexual size dimorphism in vesper bats), males tend to be redder. Also of interest is that older museum specimens tend to be the reddest, apparently because a longer history of handling has resulted in erosion of the original light-coloured or buffy tips to the hairs (Davis & Castleberry 2010).

Some hairy-tailed bats are migratory, in cases moving from southern Canada or the northern US to the far southern US. The evidence for this slowly built up from about the 1840s and has mostly been based on the seasonal appearance of large numbers of the bats in certain areas, especially on islands (to take one good example: their regular appearance on the Farallon Islands – first reported in the 1960s – only seems explainable via seasonal migration). Other bits of evidence supporting migration include observations of flocks seen moving rapidly in daylight and occasional landings on ships out at sea. Cryan (2003) also said that the several cases in which these bats have been seen to collide with buildings supported a migratory habit, though I’m not sure why: maybe because this behaviour indicates rapid flight through an unfamiliar area.

As you might expect for a group of long-distance migrants, hairy-tailed bats have been good at colonising islands: there are species within the clade that are endemic to the Galapagos Islands (L. brachyotis*), Cuba (L. pfeifferi and L. insularis) and Jamaica (L. degelidus). The Hoary bat is the supreme disperser in the group and has colonised the Hawaiian islands, appears occasionally on Iceland and Cuba, and has even managed (at least once) to get across the Atlantic and as far east as the Orkney Islands (Hill & Yalden 1990) [adjacent Hoary bat photo by BLM, from wikipedia].

* L. brachyotis is highly similar to L. borealis and was argued by Koopman & McCracken (1998) to be a subspecies of this taxon.

A fossil Eastern red bat is known from the Middle Pleistocene sediments of Bermuda – a place used today as a refuge during migration. It implies that the migratory behaviour of this species was established at least by this time (Grady & Olson 2006). Incidentally, Pliocene occurrences of both Eastern red bats and Western red bats indicate that both species have been distinct for at least 3.5 Ma (Czaplewski 1993). This provides additional evidence that they really are species rather than subspecies, as thought prior to 1988. A few other Pliocene occurrences of Lasiurus are known: an extinct species (L. fossilis) has been named from the Rexroad Formation of Kansas and also occurs in the Glenns Ferry Formation of Idaho (Czaplewski 1993) [adjacent images of Western red bat skull by David Nagorsen and Mark Brigham, from Bats of British Columbia and used in the Electronic Atlas to the Wildlife of British Columbia].

One remarkable feature of the migratory habit present in some species is that the sexes of L. cinereus (the Hoary bat) segregate in different parts of North America during the summer: females (and their young) go east, and males go west. Another unusual feature of Lasiurus bats is that females seem to typically (i.e., not just occasionally) produce more than two young at a time, and in this they are unique among bats as a whole. Litters of two or three are common, but four and five are on record too. Apparently, old records show that females used to carry their babies when they went on foraging trips, yet more modern records of such behaviour are absent. Does this really mean that behaviour has changed within the species concerned, or is it that the old records are just unreliable?

Lasiurini – what the hell kind of bats are you, really?

Hairy-tailed bats have historically been recognised as distinct at ‘tribal’ level relative to other vespertilionine vesper bats, and exactly how they might related to the other vespertilionines has yet to resolved. As I said in some of the previous articles in this series, Roehrs et al. (2010) found hairy-tailed bats to be nested within an assemblage that includes the plecotin long-eared bats; specifically, they were the sister-taxon to the American long-eared bats (Corynorhinus). This is a fairly surprising result. For one thing, it would suggest that hairy-tailed bats had secondarily evolved short ears from big-eared ancestors. This possible position is shown – in simplified form* – in the adjacent cladogram (for more discussion of the vesper bat cladogram see the article on the vesper bat cladogram).

* The cladogram depicts hairy-tailed bats and long-eared bats as if they’re sister-taxa; this isn’t technically correct for reasons just explained. I hope you can forgive me for producing a simplified, diagrammatic cladogram: for the technical, detailed version, see Roehrs et al. (2010).

Equally surprising is Agnarsson et al. (2011) recovery of hairy-tailed bats as the sister-taxon to the antrozoins (pallid bats and kin). Extremely modified, short-eared long-eared bats, or close kin to the robust-jawed, big-toothed pallid bats? As usual, more work is needed before we can be confident either way. Whatever, it doesn’t stop these neat, thick-furred, cold-tolerant, highly mobile, often migratory bats from being any less fascinating.

Comments

Dimorphism in coat colour is really rare in mammals… lemurs and gibbons come to mind.

Also, off the top of my head (and listing only such species in which the colour difference is particularly obvious): red kangaroo, banteng, nilgai, nyala, sitatunga, Nile lechwe, blackbuck, hamadryas baboon…

appears occasionally on Iceland and Cuba, and has even managed (at least once) to get across the Atlantic and as far east as the Orkney Islands

I realise that flying to Iceland from North America isn’t technically to ‘cross the Atlantic'; still, it’s a pretty respectable feat for a small bat (or rather, feats; the hoary bat is known to have reached Iceland at least four times).

Does this really mean that behaviour has changed within the species concerned, or is it that the old records are just unreliable?

Nice article Darren. I look forward to your mokele mbembe article. Have you heard Richard Freeman’s theory about it being a giant monitor lizard. He says that there are reports of them eating goats, but it seems mostly a herbivore, and an giant, omnivorous, long necked monitor lizard seems a little far fetched, especially one bigger than megalania.

One remarkable feature of the migratory habit present in some species is that the sexes of L. cinereus (the Hoary bat) segregate in different parts of North America during the summer: females (and their young) go east, and males go west.

There’s a substantial literature reporting collisions of bats with fences, TV antennae, lighthouses, the windows of buildings, vehicles and wind turbines – in fact, the Hoary bat is one of the species most affected (viz, suffering highest mortality) by wind turbines. It’s sometimes said that these accidents are due to echolocation malfunction but it also seems logical to assume that the bats are not using echolocation at the time – as David said, this would make sense during a long-haul migration flight. Orbach & Fenton (2010) showed that bats used vision when visual landmarks were available, yet suffer from poor visual acuity and are hence prone to collisions.

hairy-tailed bats roost and even hibernate outside, typically hanging from leaves or branches (roosting close to or even on the ground has been recorded too)

and

females seem to typically (i.e., not just occasionally) produce more than two young at a time, and in this they are unique among bats as a whole. Litters of two or three are common, but four and five are on record too

They roost/hibernate in the open, and they are (by bat standards) unusually fecund. Hmm. I would imagine that sleeping – never mind spending the whole winter – exposed in that way to the elements and to predators would result in high mortality; are there any such life history data for these bats?

Also, is there any satisfying explanation as for why hairy-tailed bats don’t hibernate in caves or other shelters, like typical vesper bats do?

@6: A lot of migratory birds collide with buildings too. My guess is that, as with wind turbines, the problem with some buildings is wind shear and turbulence. Bats aren’t strong fliers, and they can get sucked up by turbines. Similarly, they may get thrown into the glass by the winds around tall buildings. This could be especially true if they were migrants, not local animals familiar with an area’s hazards.

If it hasn’t been done already, this would be easy to research, starting with a correlation between weather conditions and bat/building collisions, and working up to micrometeorology on the deadliest buildings.

Yes, I remember you discussed him in a previous brilliant article coincidentally published on April 1, 2009. He seems to know his zoology, though some of the sightings he gives for modern dragons are, in my opinion, not particularly convincing. I liked the idea that monitor lizards and other large reptiles inspired dragons, but many new world dragons share many features with old world dragons. It could be something psychological, though I didn’t like An Instinct For Dragons. To many logical leaps.

Looking at the cladogram, I’m wondering whether the proposed positions of the Lasiurini are at all surprising. After all, bats show most of their diversity in their heads, so finding a lot of diversity in ear shape among sister clades isn’t that surprising. It would be somewhat useful to catalog just how much ear shape diversity is normal within tip clades in bats.

I’m a little more surprised by having epic vagrants sitting next to ground-fighters like the antrozoins, but that might just be my ignorance speaking.

Are these bats susceptible to white-nose? If they don’t nest in caves, it seems they might not get the exposure that most of the other american bat species are dropping dead from.

Are you suggesting that roosting in the open by hairy-tailed bats is an evolutionary adaptation to avoid contracting diseases from other bats? There is a problem with that idea: if the mortality risk caused by contagious disease is great enough to be an evolutionary selection force in vesper bats in general, then we should expect cave-roosting species also to be highly fecund (if anything, more so than hairy-tailed bats) in order to be able to replenish their losses. But the fact that the cave-roosting bats do, in fact, typically give birth to fewer offspring than the hairy-tailed bats suggests that roosting/hibernating in caves and other shelters is, by and large, considerably safer than roosting in the open. So the question remains: why has a (seemingly) more costly life history strategy evolved in the hairy-tailed bat clade?

Looking at the cladogram, I’m wondering whether the proposed positions of the Lasiurini are at all surprising. After all, bats show most of their diversity in their heads, so finding a lot of diversity in ear shape among sister clades isn’t that surprising. It would be somewhat useful to catalog just how much ear shape diversity is normal within tip clades in bats.

I agree that variation within ear form should not perhaps be so surprising. But I still think that the position recovered by Roehrs et al. (2010) – viz, where lasiurins are deeply nested within ‘Plecotoni’ (and not just their sister-group) – is surprising. Plecotins all have enormous, specialised ears (even the short-eared ones, like barbastelles) and have evidently ‘focused’ on the elaboration of their auditory apparatus during their evolution. Auditory specialisation is key to their hunting style, flight style and ecology. Yet the topology recovered by Roehrs et al. (2010) indicates that one plecotin lineage reversed/lost all of this, and gave rise to a group of narrow-winged, short-eared hawkers. Obviously this isn’t impossible: the morphological modifications involved – reduction in ear size, different planform – are exactly what you’d expect if this is what happened. At least some lasiurin species specialise on lepidopteran prey that are able to hear the bat’s calls: consequently, these bats appear particularly good at precisely locating their prey while in flight (Obrist & Wenstrup 1998). I’m not sure what this might mean for possible evolution from big-eared ancestors: I would guess that bigger ears would be advantageous for this sort of auditory specialisation, but then giant ears aren’t great if you’re a fast-flying hawker.

Who first suggested a monitor lizard. It would be nice if it existed, though I’m not convinced it does. Its certainly not a sauropod dinosaur. One thing creationist seem to always say is that its featured in folklore, it must exist. They don’t argue for the existence of 20 foot goat headed bats, or Anansi the Spider.

A random suggestion: perhaps the Lasiurini are an example of Allen’s Rule in bats? Air temperature decreases with elevation, and a bat that’s going to hunt high in the temperate sky is going to have to deal with some cold temperatures.

White-nose syndrome is not a generality, but a current problem: a fungus that’s affecting many North American bat populations and causing heavy mortality rates in the cave-nesting species, wiping them out during hibernation. (It would be nice if that were hyperbole, but it seems to not be, judging by the articles.) It’s sad and horrifying and the scientists trying to deal with it are woefully understaffed, underequipped and underfunded.

Curiously, similar strains of fungus have been found in european bat populations, but they don’t seem to be having the same catastrophic effect. American bat species seem to be crashing, much like american honeybees.

The thing about white-nose, though, is that it seems to be specific to caves and hibernators.(it spreads cave-to-cave with migrations). That’s why I was asking if hoary bats were affected by it. Mr. Naish seems like the person to ask.

You have got me intrigued about the “extinction” of the Galapagos Lasiurus. I could not track any data about that

I wondered about that too. According to this site, the Galapagos bat is not only extant but in the ‘Least Concern’ category.

Nice Ogress:

That’s why I was asking if hoary bats were affected by it. Mr. Naish seems like the person to ask.

If I understood him right, Darren will deal with conservation issues (including the white-nose syndrome) in some detail in the last part of this epic vesper bat series. He’ll have to go through the several remaining vespertilionid clades before that, though, so we’ll have to wait. But be patient and he will deliver.

My most burning question here is what is up with the bat cranium. Is there no work on bat neurobiology? Is a significant encephalization quotient for vespertines (all microbats?) simply to keep up with processing the noisy information one gets from subaerial sonar? How does that information-processing requirement compare with marine echolocation? Or are bats just little web-winged brainiacs?

My two cents…there could be some interesting comparative neurobiology there.

This source states that L. brachyotis isn’t even endemic to the Galapagos Islands

Did you see Darren’s footnote in the OP? There he wrote:

L. brachyotis is highly similar to L. borealis and was argued by Koopman & McCracken (1998) to be a subspecies of this taxon.

(You can look this up yourself in the Koopman & McCracken paper which, if I’m not much mistaken, is open access.)

In other words, this issue is a matter of classification, where there ultimately are no ‘right’ or ‘wrong’ answers – something that we’ve discussed here on Tet Zoo countless times before.

In this case, a bat systematist would have (at least) three alternatives:

1) To not recognise brachyotis as a valid subspecies at all: in that case, you can say that “The species Lasiurus borealis is not endemic to the Galapagos Islands”.

2) To treat brachyotis as a subspecies of borealis: in that case, you can say that “The species Lasiurus borealis as a whole is not endemic to the Galapagos Islands, but the subspecies Lasiurus borealis brachyotis is”. (Koopman & McCracken took this view in 1998.)

3) To recognise brachyotis as a separate species: in that case, you can say that “The species Lasiurus brachyotisis endemic to the Galapagos Islands” (whereas the species Lasiurus borealis does not occur there).

As I said, we’ve had this kind of discussion many times before on this blog (and we will surely have it many more times again). These days many of us (including, AFAIK, Darren) are not big fans of the concept of ‘subspecies’ and are increasingly inclined to abandon it altogether. In that case, it would become a choice between my above alternatives 1) and 3), respectively. If these Galapagos bats are ‘distinct enough’ from the mainland Lasiurus borealis to warrant recognition as a separate taxon (and many if not most authorities would seem to agree that they are) the logical choice would then be to treat them as a separate species, i.e., Lasiurus brachyotis (which then becomes a species endemic to the Galapagos Islands).

Metridia (comment 23): it’s been said that there is more literature correlating bat brain size and anatomy with body size/ecology/life history variables that than of any other animal group excepting primates and birds. In fact, there’s a three-volume series of books on bat neurobiology, all titled (as vols 1, 2 and 3, respectively)…

And there are an awful lots of specific studies on various aspects of bat brain anatomy and biology… the literature on such things as how bats can afford the big brains they have, hippocampus function and neurogenesis, and how brain size is related to mating systems, navigational abilities and spatial memory is substantial. Echolocating bats have proportionally large cerebella compared to other mammals (except cetaceans) (Clark et al. 2001), presumably because it provides extra ‘processing power’ for sophisticated sensory abilities (the most likely explanation for the huge brains of mormyrid fish, by the way). However, fruit bats have particularly big brains overall – bigger than those of ‘microbats’ (Jones & MacLarnon 2004). It’s been widely suggested that bat brains are big because of flight, and/or because of the 3D spatial awareness required for their foraging style, but correlations with diet have been reported in some studies (fruit eaters can afford bigger brains), as have correlations with female mate fidelity and testes size! A really neat subject that deserves more attention than this one brief comment…

Hi Dartian, thanks for your comments. However, they are irrelevant since I should not have said ‘endemic’ but rather ‘native’, which inadvertently gave everybody the wrong impression, for which I apologize. But if you read the sentence I referred to, you would have realized this fact.

The source basically states that L. (borealis) brachyotis is an alien (sub)species, which has taken up residence in the Galapagos islands.

Lasiurus brachyotis: when researching this article, I’m sure I saw something saying that the endemic Galapagos bat was extinct. Can’t find it now, and have to assume that I made a mistake. Sorry for confusion. I’m going to modify the text now.

Two bat species Lasiurus brachyotis and L. cinereus also have made it to the islands, and they are not endemic.

It is perfectly possible for a species to be both ‘native’ and ‘not endemic’ to some particular place. For example, the leopard is native to both Africa and to Eurasia, but is endemic to neither. (One could, however, say that the leopard is endemic to the Old World.)

The source basically states that L. (borealis) brachyotis is an alien (sub)species, which has taken up residence in the Galapagos islands.

Trivially true. By that logic, all organisms on the Galapagos Islands are basically ‘aliens’ there. All of their ancestors came from somewhere else at some point (and, geologically speaking, often surprisingly recently too).

Hi Dartian, L. brachyotis “made it” to the Galapagos Islands which means that it did not evolve their. Rather it evolved somewhere else (Ecuador or a close South American country)and has now taken up residence their. So, even if it is now considered to be “native” it is not native in the true sense of having evolved in situ (at least according to the stated source). That is the sense in which I meant, which perhaps in hindsight I can see may lead to some confusion. However, I stand by my previous statement.

But that is not the sense in which ‘native’ is normally understood and used by biologists. Any organism that has been able to spread to and to establish itself in any place on this planet by natural means (that is, not assisted by human beings either directly or indirectly) is considered ‘native’ there. There is no must-have-evolved-in-situ requirement. Sorry, but you just can’t invent your own idiosyncratic terminology and expect to be understood by others – unless, of course, you actually want to get misunderstood (in which case your ideas will eventually just end up being ignored by everyone else).

I stand by my previous statement

You shouldn’t, because the reasoning behind your statement was not particularly sound.

I agree with Dartian. Because these arguments come up frequently with the native plants I work with (western US), many botanists have arbitrarily declared that “native” means that all evidence suggests that it was growing wild here in 1491. For those who aren’t Yanks, Columbus landed in 1492.

It’s quite useful to include time when discussing endemism. For example, I’ve seen a serious (and deluded) proposal to plant redwoods in a semi-desert city. The argument was that they grew in the desert during the Miocene. Therefore they are native to the desert, and it was totally appropriate to plant them as a restoration effort.

Thanks for the answer Darren. I think this are great news after all, a tropical bat not extinct.I check also de Koopman & MacKracken paper, the taxonomy I think is not clear enough. Probably a major phylogenetic analysis is requiered considering that Antillean “subespecies” seems to be different species. Other tetrapod taxa from Galapagos shows Antillean affinities and appear to be distinctive species (Tyto punctatissima come to my mind). To clarify this situation seems very important for conservation because of the limited distribution of the bat in the islands.

I haven’t been aware that the idea to put a time period to endemism. Historic times (e. g. 1492)seem comprensible, but to include geologic periods!!! I am sorry, but I find the idea really weird.